The overall goal of this proposal is to identify the neural mechanisms underlying changes associated with Mindfulness-Based Stress Reduction (MBSR). Clinical research has shown that MBSR reduces psychological distress and increases well-being, but the mechanisms underlying these changes in not well described. Basic research has examined the neural bases of emotion and emotion regulation, but this research has not examined changes following MBSR. To integrate clinical and basic research literatures, we employ a translational framework that characterizes the impact of MBSR on emotion regulation in terms of interactions between ventral emotion-generative brain regions and dorsal emotion-regulatory brain regions. Within this framework, we propose to compare the effects of MBSR and an active control condition (ACC) in participants with generalized social phobia (SP). SP will be randomly assigned to MBSR or ACC and assessed using self-report inventories and functional magnetic resonance imaging (fMRI) before and after MBSR and the ACC. Three aims will be investigated: Aim 1 investigates the effects of MBSR on anxiety and well-being. For the MBSR participants, we expect significant (a) decreases in anxiety, and (b) increases in well-being at immediately post-intervention and at the 3-month follow-up compared to pre-intervention. For the ACC participants, we expect no change in anxiety or well-being from pre- to post-intervention. Aim 2 investigates the effects of MBSR on attentional and cognitive emotion regulation. We expect MBSR participants to show improvements in attentional regulation (the focus of MBSR), but no change in cognitive regulation (not the focus of MBSR) from pre- to post-intervention, as indicated by (a) greater reductions in negative emotion ratings, (b) greater reductions in ventral emotion-generative brain regions, as well as (c) greater increases in attention-related dorsal emotion-regulatory brain regions. We do not expect ACC participants to show changes in either form of regulation from pre- to post-ACC. Aim 3 investigates whether MBSR-related changes in attentional emotion regulation mediate MBSR treatment response (decreases in anxiety and increases in well-being) at post-treatment and at the 3-month follow-up.